Briquettes, especially of naturally moist biomass, should be storable and suitable for use as bio-fuel. In the apparatus which, for example, consists of at least one chopper and at least one screw press, the charged biomass is comminuted to a defined particle size. The comminuted material is intimately mixed with a non-oxidised plastic microcrystalline wax (recycling wax) before it is forced via the screw press into a compaction chamber to form at least one briquette. In the case of biomasses having relatively high moisture contents, especially naturally moist biomasses, an inorganic adsorbent, especially sodium or potassium aluminosilicate, which is compatible with the microcrystalline wax, is admixed for binding the moisture before blending with wax.